This independent scientist award (K02) is proposed for the applicant to acquire necessary skills for enhancing work on the developmental pathways of adolescent drug use behaviors including substance use disorders (SUD), with a particular focus on long-term pathways. The intensive period of study afforded by a K02 will permit the applicant to gain scientific skills via coursework, workshops and consultations with experts in the field. Specifically, the career development plan will enhance the analysis of current data and the development of future studies of existing prospective samples by focusing on the acquisition of a thorough foundation in (a) advanced statistical modeling techniques and related methodological issues; (b) the theoretical underpinnings and relevant models associated with young adulthood, the development period from the late teens through the twenties; and (c) the role of innovative brief intervention strategies as relapse prevention strategies for youth who are recovering from a prior substance use disorder. The enhanced statistical skills will be applied to prospective longitudinal data sets at the University of Minnesota, as well as other national data sets. The local data represent two youth groups: an at-risk group and a substance use disorder (SUD) group. The at-risk group consists of teenagers who were diagnosed with ADHD, Conduct Disorder (CD)/Oppositional Defiant Disorder (ODD) or both during childhood. Some of these youth have either developed an SUD during adolescence whereas others are at-risk for developing a later-onset SUD. The second data set, the SUD group, consists of adolescents who were diagnosed with and treated for a SUD as a teenager and for whom ADHD and CD/ODD are common comorbidities. This latter group is relevant to the study of the course of SUD as the youth age toward young adulthood. Both samples have normal groups matched on age, gender, race, and SES fo use in comparative analyses. Based on empirical findings to date, the specific hypotheses focus on externalizing disorders (e.g. ADHD and CD/ODD) as possible predictors, consequences, or moderators of the developmental pathways of adolescent drug use behaviors. Select personal (psychological distress) and environmental (drug use by peers, parenting practices, and treatment experiences) factors will be considered in hypothesis testing as well. The aims of this award will advance research on the cause and consequences of adolescent substance use disorders by clarifying the role of disruptive behaviors, and the award will help enhance the investigator's skills in researching the long-term course of adolescents who are either at-risk for developing an SUD or have experienced an adolescent-onset SUD.